RANGE / ENDURANCE
Range = distance on the amount of fuel available Endurance = time on the amount of fuel available
Piston Engine (Power vs speed)
ENDURANCE: fuel flow is approximately proportional to power setting => max endurance = speed for minimum power
Speed for maximum endurance = VMP (minimum power)
RANGE: max range sped is found where the ration between TAS and Power required is maximum
TAS
SR=
SFC x power required
Jet Aircraft (Drag (=thrust) vs speed)
ENDURANCE: fuel flow is approximately proportional to thrust setting. Speed for maximum endurance is found when
thrust required to maintain flight level is minimum
Speed for maximum endurance = VMD (minimum drag)
RANGE: max range sped is found where the ration between TAS and drag is maximum
TAS
SR=
SFC x Drag
Effects of variables on Endurance and Range
Wind :
Speed for max ENDURANCE: does not affect speed for max endurance (only criteria measured is flying time)
Speed for best RANGE: increases with headwind, decreases with tailwind
Aircraft Mass:
If the mass increases, drag and power required increase => higher fuel flow and reduction of specific range
With a higher mass, endurance and range decrease and speed have to increase
Speed for max ENDURANCE: increases with mass increases
Speed for max RANGE: increases with mass increases
Altitude:
JET ENDURANCE: Endurance increases when altitude increases until reaching the optimum altitude. Above optimum
altitude, endurance decreases (compressibility drag).
JET RANGE: Range increases when altitude increases until reaching the optimum altitude (TAS and engine efficiency
increase). Above optimum altitude, range decreases (compressibility drag).
PROP ENDURANCE: with altitude increases, SFC improves but power required increases => Endurance remains constant
PROP RANGE: with altitude increases, SFC improves and TAS to power required ratio remains pretty constant.
Endurance increases slightly.
Temperature:
Increased temperature results in a higher TAS but lower engine efficiency.
RANGE: remains constant.
ENDURANCE: decreases with altitude increases due to SFC negatively affected.